Extractor hood
An extractor hood (technical term: vapor extraction ) is a device for extracting and filtering the vapors (cooking or baking fumes ) that arise during cooking .
There are two modes of operation:
- Exhaust air - the vapor is passed through a grease filter and passed out of the house through generously sized pipes (125 mm diameter or 150 mm (now standard)). The connection of this pipe to the outside can be made with a wall box .
- Circulating air - The vapor is passed through the grease filter and the odor filter andreturned to the room. This type of operation isrecommendedfor low-energy houses and passive houses . Very inexpensive models only have one grease filter.
Extractor hoods serve three main purposes:
- Separation of fat from the vapor that arises during cooking and frying so that it does not condense in the room. The grease settles on filter fleece or metal mesh or is separated in air vortices by centrifugal force. A pure exhaust air system without a grease filter or separator is also possible. In this case, the ventilation pipes must be made grease-tight and regularly freed from deposited grease or completely replaced. Fat deposits on fire are difficult to extinguish. Without an extractor hood, the grease from the room air is deposited on objects, furniture, walls and ceilings, which shortens the intervals between necessary cleaning and renovation measures.
- Filtering cooking smells from the room air, if this is desired. If the ventilation through open windows is insufficient to remove odors from the kitchen air, this can be done efficiently using an exhaust system. A recirculation system must be equipped with an activated carbon filter in order to filter out odors to a large extent. Activated carbon filters usually have to be replaced or regenerated after a few months. In the test, activated carbon filters remove between 40 and 85% of the flavoring substances used.
- Removal of the water vapor produced during cooking and baking . The amount of moisture to be removed varies considerably depending on the cooking habits. Without an exhaust air extractor hood, a large part of the water vapor is temporarily absorbed by wall and ceiling surfaces and then has to be ventilated gradually so as not to condense as condensation on the coldest parts of the wall . Unless this is done via a leaky building envelope or a central ventilation system , the humidity can only be removed through an extractor hood in exhaust air mode.
The first range hood for domestic use was developed and brought onto the market by Vent-A-Hood in the USA in the 1940s.
Components of an extractor hood
- Grease filters , in the past, disposable fleece mats were often used, but now inserts with metal mesh that can be cleaned in the dishwasher predominate
- Odor filters generally contain activated carbon . There are regenerable and so - called maintenance - free activated carbon filters that are disposed of after use. Fleece mats can only hold back a small proportion of odors.
- Blower , either inside the housing of the hood or as an external suction through a z. B. fan installed on the roof or on an external wall
- workplace lighting is often integrated in the housing
- Blow-out openings in recirculation mode and connecting pieces for the ventilation duct for exhaust air mode
Executions
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Most of the extractor hoods can now be used in either recirculation or exhaust air mode.
The following device designs are used:
- Built-in hood, which is largely contained in a kitchen wall cabinet
- Undermount hood as the most common type. Often designed flat and intended for assembly below or in a wall cabinet, which is then also called a vaporizer cabinet. In exhaust air mode, the exhaust air hose is led up through the cabinet. Inexpensive extractor hoods are typically 60 cm wide and 50 to 55 cm deep and offer an air flow rate in recirculation mode between 80 and 200 m³ / h.
- Wall hood for attachment to the wall. Free-hanging wall hoods are also known as chimney hoods . In contrast to built-in hoods, these are typically made of stainless steel, are significantly more expensive, 90 cm wide and 45 to 55 cm deep and offer an air flow rate of between 80 and 400 m³ / h in recirculation mode.
- Island hood for free attachment to the ceiling
- Ceiling fan
- Flat screen hood
- Downdraft fan / cooktop extractor. In the domestic area, extractor hoods that are integrated in the base cabinet and whose extraction openings are in the worktop on the side of the hob are still not very common. In some cases, suction nozzles can be moved out of the worktop electrically
- Fan module with separate hood
Headroom hoods rise towards the center of the room so as not to restrict the view of the hob.
In intensively used commercial kitchens, kitchen exhaust air ceilings are also installed, which extend from wall to wall and can be set up in such a way that the calculated air volumes can be extracted flexibly above the respective source.
To achieve a more powerful or quieter extraction, external fans are used:
- Exterior wall fans are attached to the outside of the exterior wall
- Built-in wall fans are used in (telescopic) wall boxes
- Roof blowers for pitched and flat roofs differ in design. On the pitched roof, the fan should be installed in the slipstream of the prevailing wind direction in order to avoid air back pressure.
- Inter-chamber blowers are installed anywhere along the air duct.
If exhaust air ducts are routed into other rooms or through the ceiling, thermally triggering fire dampers should be provided, especially in apartment buildings, in order to prevent the rapid spread of fire and smoke in the event of a fire.
Grease filter
Fleece filters in mat form can be cut to size yourself. They usually consist of either densely packed cellulose , rayon or polyester fibers that are one millimeter thick or a polyester braid that is five millimeters thick. Some nonwovens contain a visual indicator that shows the amount of fat absorbed by showing a fat-soluble dye on the surface of the mat. Typically, a fleece filter has to be replaced and disposed of after one to three months.
Mesh filters consist of several layers of aluminum or stainless steel braiding and are joined together to form a cassette using a surrounding frame. The inert fat particles in multiple changes of direction of the air flowing through by the centrifugal force directed to the braid and adhere there. The effectiveness depends not only on the strength of the filter, but also on the shape of the mesh and the flow speed. The cassette is preferably held in the device by a circumferential magnetic strip, which at the same time enables a reliable seal.
The filters can easily be cleaned in the dishwasher. If dirty dishes are cleaned in the machine at the same time, food residues can settle in the filter. Aluminum filters are often discolored by the alkaline cleaning agents, which usually hardly affects the durability of the filters. We recommend cleaning after 15 to 40 hours of operation, but at the latest after two to four weeks. Some fats can harden over time and can then hardly be removed from the filter with household means. The same applies to hardening oils such as sunflower oil . If hot fat catches fire on the stove, the fat-laden filters can also ignite and spread the fire through the exhaust duct.
Even with labyrinth filters and centrifugal separation , water, fat and oil particles are separated from the cooking vapors by centrifugal force while the air is being swirled. Centrifugal separation works without a grease filter. The liquid particles collide with the wall of the air duct and can be wiped off from there. Larger quantities of grease that accumulate in extractor hoods for commercial kitchens run together in a collecting vessel and can be drained off from there.
Several manufacturers refer to several filters placed one behind the other as cascade filters.
Odor filter
Since fleece filters can hardly bind odors, circulating air devices are usually equipped with activated carbon filters that are used as cassettes in the device.
In order to distribute the activated carbon evenly, filters with loosely filled granules should be gently shaken before use.
Activated carbon filters should be regenerated or replaced after 120 to 200 operating hours or after 3 to 12 months and disposed of with household waste.
Some regenerable filters can be regenerated by heating them in the oven. Others are cleaned in the dishwasher at up to 65 ° C and then dried in the oven. Regenerative filters should be replaced after about three years as their effectiveness deteriorates over time.
Activated charcoal filters should never be operated without a separate grease filter, otherwise they will quickly clog. After cooking, the extractor hood should run for ten to twenty minutes to dry the damp activated charcoal again.
business
Newly constructed buildings have increasingly been made airtight since the 1990s. In order to effectively discharge the kitchen air, air must be allowed to enter via a ventilation system or via an open window. It is recommended to open a window on the opposite wall when operating the extractor hood. Air that enters through the side windows flows across the stove and can lead the vapor away from the extractor hood.
If there is a room air-dependent fireplace in the apartment , such as a gas floor heating system, a gas water heater, an open fireplace, a tiled stove or a wood-burning stove , special measures are required when operating an extractor hood to ensure that no combustion gases enter the Spaces are vacuumed. In the simplest case, a contact switch on the window allows the fan to operate only when the window is open.
hygiene
Every cooker hood must be cleaned regularly for the best possible cleaning effect. Over-greased grease filters that have not been cleaned for a long time pose a fire hazard. The following applies to clean extractor hoods: Clean the grease filter once a month.
In the catering sector, VDI 6022 applies to hygiene inspections and EC regulation No. 852/2004 on hazard analysis and critical control points (HACCP), which is primarily responsible for the design of the ventilation technology.
Design and assembly
The maximum air output of the extractor hood should be roughly 12 times the room volume.
A distance of 60 cm to the lower edge of the extractor hood is often assumed above electric hobs. In order not to reduce the effectiveness of the extractor, a stronger extractor should also be selected if the distance is greater. In general, a distance of 90 cm should not be exceeded. If only people of average height use the hob, a distance of 55 cm may be sufficient with a hood that is only 45 cm deep. With a typical work surface height of 82 to 86 cm, the installation height of the lower edge of the device is at least 137 cm and at most 175 cm, with a standard dimension of around 145 cm. The electrical connection can be provided about 10 cm above. Only people who are taller than 175 cm use the hob, larger dimensions may be assumed.
In order to reduce the risk of grease deposited in the extractor hood igniting, the distance to the lower edge of the extractor hood should be at least 65 cm on gas hobs.
The extractor hood should be about 10 cm wider on both sides than the hob. From the outer edge of the hob to the outer edge of the hood, there should be an angle of 5 ° to 8 ° with respect to the perpendicular . If a draft across the hob is to be expected more frequently, as is the case with free-standing cooking islands, the overhang of the extractor hood should be increased to 15 to 20 cm on both sides. The corresponding angle is 10 ° to 12 °.
If an overhang of the hood is not desired, an extractor hood can be selected as an alternative, in which the suction is not evenly distributed over the entire surface, but primarily only at the edge.
See also
Web links
Individual evidence
- ↑ a b c Extractor hoods - first fogged, then evaporated , Stiftung Warentest, April 25, 2002
- ↑ a b c Brochure Electrolux extractor hoods - Basics for planning and sales , In: Electrolux.ch
- ↑ a b c d e f Expertise on extractor hoods , section "Exhaust air needs supply air!", In: HEA.de
- ↑ legal regulation www.kratz-ug.de, accessed on August 28, 2013
- ↑ Planning tips - More ergonomics in the kitchen: The right kitchen dimensions, In: Kueche-Co.de, © 2019 Küche & Co GmbH